Photoresist composition and method of forming photoresist pattern

ABSTRACT

A photoresist composition includes a photoresist material including metal oxide nanoparticles and a ligand, and an acid having an acid dissociation constant, pKa, of −15&lt;pKa&lt;4, or a base having a pKa of 40&gt;pKa&gt;9.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/685,677, filed Jun. 15, 2018, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to photoresist compositions and methods of forming photoresist patterns in a semiconductor manufacturing processes.

BACKGROUND

As consumer devices have gotten smaller and smaller in response to consumer demand, the individual components of these devices have necessarily decreased in size as well. Semiconductor devices, which make up a major component of devices such as mobile phones, computer tablets, and the like, have been pressured to become smaller and smaller, with a corresponding pressure on the individual devices (e.g., transistors, resistors, capacitors, etc.) within the semiconductor devices to also be reduced in size.

One enabling technology that is used in the manufacturing processes of semiconductor devices is the use of photosensitive materials. Such materials are applied to a surface and then exposed to an energy that has itself been patterned. Such an exposure modifies the chemical and physical properties of the exposed regions of the photosensitive material. This modification, along with the lack of modification in regions of the photosensitive that were not exposed, can be exploited to remove one region without removing the other.

However, as the size of individual devices has decreased, process windows for photolithographic processing have become tighter and tighter. As such, advances in the field of photolithographic processing are necessary to maintain the ability to scale down the devices, and further improvements are needed in order to meet the desired design criteria such that the march towards smaller and smaller components may be maintained.

Extreme ultraviolet lithography (EUVL) has been developed to form smaller semiconductor device feature size and increase device density on a semiconductor wafer. As device features shrink the elimination of defects becomes more critical. Defects may be formed by variation of sensitivity and exposure tolerance of the photoresist. Some embodiments of photoresist compositions have a limited shelf life. As a photoresist compositions age, the sensitivity and exposure tolerance of the photoresist varies, leading to variations in the patterns formed, and subsequently defects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a process flow of manufacturing a semiconductor device according to embodiments of the disclosure.

FIG. 2 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 3 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 4 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 5 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 6 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 7 shows photoresist polymer components according to embodiments of the disclosure.

FIG. 8 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 9 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 10 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 11 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 12 shows a process stage of a sequential operation according to an embodiment of the disclosure.

FIG. 13 shows a process stage of a sequential operation according to an embodiment of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Specific embodiments or examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, dimensions of elements are not limited to the disclosed range or values, but may depend upon process conditions and/or desired properties of the device. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Various features may be arbitrarily drawn in different scales for simplicity and clarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. In addition, the term “made of” may mean either “comprising” or “consisting of.”

Increased actinic radiation absorption improves photolithographic patterning processes. Metal oxides absorb a greater amount of radiation, such as extreme ultraviolet radiation, than organic molecules. Metal oxide nanoparticles are added to photoresists to improve absorption of actinic radiation, such as extreme ultraviolet radiation. To prevent the metal oxides from separating from the photoresist composition, the metal oxides are complexed by ligands forming a ligand/metal complex. However, the ligand/metal complex is not stable in some photoresist compositions. Initially, each metal oxide nanoparticle may complexed by a plurality of ligand molecules. Over a period of time the photoresist composition ages, ligand molecules separate from the ligand/metal complex, and the insufficiently complexed or uncomplexed metal oxide nanoparticles may separate from the photoresist composition. It is desirable to inhibit or prevent photoresist aging.

FIG. 1 illustrates a process flow 100 of manufacturing a semiconductor device according to embodiments of the disclosure. A photoresist is coated on a surface of a layer to be patterned or a substrate 10 in operation S110, in some embodiments, to form a photoresist layer 15, as shown in FIG. 2. Then the photoresist layer 15 undergoes a first baking operation S120 to evaporate solvents in the photoresist composition in some embodiments. The photoresist layer 15 is baked at a temperature and time sufficient to cure and dry the photoresist layer 15. In some embodiments, the photoresist layer is heated to a temperature of about 40° C. to 200° C. for about 10 seconds to about 10 minutes.

After the first baking operation S120, the photoresist layer 15 is selectively exposed to actinic radiation 45 (see FIG. 3) in operation S130. In some embodiments, the photoresist layer 15 is selectively exposed to ultraviolet radiation. In some embodiments, the ultraviolet radiation is deep ultraviolet radiation. In some embodiments, the ultraviolet radiation is extreme ultraviolet (EUV) radiation. In some embodiments, the radiation is an electron beam.

As shown in FIG. 3, the exposure radiation 45 passes through a photomask 30 before irradiating the photoresist layer 15 in some embodiments. In some embodiments, the photomask 30 has a pattern to be replicated in the photoresist layer 15. The pattern is formed by an opaque pattern 35 on photomask substrate 40, in some embodiments. The opaque pattern 35 may be formed by a material opaque to ultraviolet radiation, such as chromium, while the photomask substrate 40 is formed of a material that is transparent to ultraviolet radiation, such as fused quartz.

The region 50 of the photoresist layer exposed to radiation 45 undergoes a chemical reaction thereby changing its solubility in a subsequently applied developer relative to the region 52 of the photoresist layer 15 not exposed to radiation. In some embodiments, the region 50 of the photoresist layer exposed to radiation 45 becomes more soluble in the developer. In other embodiments, the region 50 of the photoresist layer exposed to radiation 45 becomes less soluble in the developer. In some embodiments, the region 50 of the photoresist layer 15 exposed to radiation undergoes a crosslinking reaction. In other embodiments, the region 50 of the photoresist layer 15 does not undergo a crosslinking reaction. In some embodiments, the region 50 of the photoresist layer 15 that undergoes a crosslinking reaction is less soluble in a developer. In some embodiments, even though the region 50 of the photoresist exposed to radiation 45 undergoes a crosslinking reaction it is more soluble in certain developers, as will be explained herein.

Next the photoresist layer 15 undergoes a post-exposure bake in operation S140. In some embodiments, the photoresist layer 15 is heated to a temperature of about 50° C. and 160° C. for about 20 seconds to about 120 seconds. The post-exposure baking may be used in order to assist in the generating, dispersing, and reacting of the acid/base/free radical generated from the impingement of the radiation 45 upon the photoresist layer 15 during the exposure. Such assistance helps to create or enhance chemical reactions which generate chemical differences between the exposed region 50 and the unexposed region 52 within the photoresist layer 15. These chemical differences also caused differences in the solubility between the exposed region 50 and the unexposed region 52.

The selectively exposed photoresist layer 15 is subsequently developed by applying a developer to the selectively exposed photoresist layer in operation S150. As shown in FIG. 4, a developer 57 is supplied from a dispenser 62 to the photoresist layer 15. In some embodiments, the exposed portion 50 of the photoresist layer 50 is removed by the developer 57 forming a pattern of openings 55 in the photoresist layer 15 to expose the substrate 20, as shown in FIG. 5. In other embodiments, the unexposed regions 52 of the photoresist layer are removed by the developer 57, thereby forming a pattern.

In some embodiments, the pattern of openings 55 in the photoresist layer 15 are extended into the layer to be patterned or substrate 10 to create a pattern of openings 55′ in the substrate 10, thereby transferring the pattern in the photoresist layer 15 into the substrate 10, as shown in FIG. 6. The pattern is extended into the substrate 10 by etching, using one or more suitable etchants. The unexposed photoresist layer 15 is at least partially removed during the etching operation in some embodiments. In other embodiments, the unexposed photoresist layer 15 is removed after etching the substrate 10 by using a suitable photoresist stripper solvent or by a photoresist ashing operation.

In some embodiments, the substrate 10 includes a single crystalline semiconductor layer on at least it surface portion. The substrate 10 may include a single crystalline semiconductor material such as, but not limited to Si, Ge, SiGe, GaAs, InSb, GaP, GaSb, InAlAs, InGaAs, GaSbP, GaAsSb and InP. In some embodiments, the substrate 10 is a silicon layer of an SOI (silicon-on insulator) substrate. In certain embodiments, the substrate 10 is made of crystalline Si.

The substrate 10 may include in its surface region, one or more buffer layers (not shown). The buffer layers can serve to gradually change the lattice constant from that of the substrate to that of subsequently formed source/drain regions. The buffer layers may be formed from epitaxially grown single crystalline semiconductor materials such as, but not limited to Si, Ge, GeSn, SiGe, GaAs, InSb, GaP, GaSb, InAlAs, InGaAs, GaSbP, GaAsSb, GaN, GaP, and InP. In an embodiment, the silicon germanium (SiGe) buffer layer is epitaxially grown on the silicon substrate 10. The germanium concentration of the SiGe buffer layers may increase from 30 atomic % for the bottom-most buffer layer to 70 atomic % for the top-most buffer layer.

In some embodiments, the substrate 10 includes at least one metal, metal alloy, and metal/nitride/sulfide/oxide/silicide having the formula MX_(a), where M is a metal and X is N, S, Se, O, Si, and a is from about 0.4 to about 2.5. In some embodiments, the substrate 10 includes titanium, aluminum, cobalt, ruthenium, titanium nitride, tungsten nitride, tantalum nitride, and combinations thereof.

In some embodiments, the substrate 10 includes a dielectric having at least silicon, metal oxide, and metal nitride of the formula MX_(b), where M is a metal or Si, X is N or O, and b ranges from about 0.4 to about 2.5. Ti, Al, Hf, Zr, and La are suitable metals, M, in some embodiments. In some embodiments, the substrate 10 includes silicon dioxide, silicon nitride, aluminum oxide, hafnium oxide, lanthanum oxide, and combinations thereof.

The photoresist layer 15 is a photosensitive layer that is patterned by exposure to actinic radiation. Typically, the chemical properties of the photoresist regions struck by incident radiation change in a manner that depends on the type of photoresist used. Photoresist layers 15 are typically positive resists or negative resists. Positive resist refers to a photoresist material that when exposed to radiation (typically UV light) becomes soluble in a developer, while the region of the photoresist that is non-exposed (or exposed less) is insoluble in the developer. Negative resist, on the other hand, refers to a photoresist material that when exposed to radiation becomes insoluble in the developer, while the region of the photoresist that is non-exposed (or exposed less) is soluble in the developer. The region of a negative resist that becomes insoluble upon exposure to radiation may become insoluble due to a cross-linking reaction caused by the exposure to radiation.

Whether a resist is positive or negative may depend on the type of developer used to develop the resist. For example, some positive photoresists provide a positive pattern, (i.e.—the exposed regions are removed by the developer), when the developer is an aqueous-based developer, such as a tetramethylammonium hydroxide (TMAH) solution. On the other hand, the same photoresist provides a negative pattern (i.e.—the unexposed regions are removed by the developer) when the developer is an organic solvent. Further, in some negative photoresists developed with the TMAH solution, the unexposed regions of the photoresist are removed by the TMAH, and the exposed regions of the photoresist, that undergo cross-linking upon exposure to actinic radiation, remain on the substrate after development. In some embodiments of the present disclosure, a negative photoresist is exposed to actinic radiation. The exposed portions of the negative photoresist undergo crosslinking as a result of the exposure to actinic radiation, and during development the exposed, crosslinked portions of the photoresist are removed by the developer leaving the unexposed regions of the photoresist remaining on the substrate.

In an embodiment, the photoresist layer 15 is a negative photoresist that undergoes a cross-linking reaction upon exposure to the radiation. Photoresists according to the present disclosure include a polymer resin along with one or more photoactive compounds (PACs) in a solvent, in some embodiments. In some embodiments, the polymer resin includes a hydrocarbon structure (such as an alicyclic hydrocarbon structure) that contains one or more groups that will decompose (e.g., acid labile groups) or otherwise react when mixed with acids, bases, or free radicals generated by the PACs (as further described below). In some embodiments, the hydrocarbon structure includes a repeating unit that forms a skeletal backbone of the polymer resin. This repeating unit may include acrylic esters, methacrylic esters, crotonic esters, vinyl esters, maleic diesters, fumaric diesters, itaconic diesters, (meth)acrylonitrile, (meth)acrylamides, styrenes, vinyl ethers, combinations of these, or the like.

Specific structures that are utilized for the repeating unit of the hydrocarbon structure in some embodiments, include one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, acetoxyethyl acrylate, phenyl acrylate, 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-alkyl-2-adamantyl (meth)acrylate or dialkyl(1-adamantyl)methyl (meth)acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, acetoxyethyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-(2-methoxyethoxy)ethyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, 3-acetoxy-2-hydroxypropyl methacrylate, 3-chloroacetoxy-2-hydroxypropyl methacrylate, butyl crotonate, hexyl crotonate, or the like. Examples of the vinyl esters include vinyl acetate, vinyl propionate, vinyl butylate, vinyl methoxyacetate, vinyl benzoate, dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, acrylamide, methyl acrylamide, ethyl acrylamide, propyl acrylamide, n-butyl acrylamide, tert-butyl acrylamide, cyclohexyl acrylamide, 2-methoxyethyl acrylamide, dimethyl acrylamide, diethyl acrylamide, phenyl acrylamide, benzyl acrylamide, methacrylamide, methyl methacrylamide, ethyl methacrylamide, propyl methacrylamide, n-butyl methacrylamide, tert-butyl methacrylamide, cyclohexyl methacrylamide, 2-methoxyethyl methacrylamide, dimethyl methacrylamide, diethyl methacrylamide, phenyl methacrylamide, benzyl methacrylamide, methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethyl vinyl ether, or the like. Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl methyl benzoate, α-methyl styrene, maleimide, vinylpyridine, vinylpyrrolidone, vinylcarbazole, combinations of these, or the like.

In some embodiments, the repeating unit of the hydrocarbon structure also has either a monocyclic or a polycyclic hydrocarbon structure substituted into it, or the monocyclic or polycyclic hydrocarbon structure is the repeating unit, in order to form an alicyclic hydrocarbon structure. Specific examples of monocyclic structures in some embodiments include bicycloalkane, tricycloalkane, tetracycloalkane, cyclopentane, cyclohexane, or the like. Specific examples of polycyclic structures in some embodiments include adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like.

The group which will decompose, otherwise known as a leaving group or, in some embodiments in which the PAC is a photoacid generator, an acid labile group, is attached to the hydrocarbon structure so that, it will react with the acids/bases/free radicals generated by the PACs during exposure. In some embodiments, the group which will decompose is a carboxylic acid group, a fluorinated alcohol group, a phenolic alcohol group, a sulfonic group, a sulfonamide group, a sulfonylimido group, an (alkylsulfonyl) (alkylcarbonyl)methylene group, an (alkylsulfonyl)(alkyl-carbonyl)imido group, a bis(alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imido group, a bis(alkylsylfonyl)methylene group, a bis(alkylsulfonyl)imido group, a tris(alkylcarbonyl methylene group, a tris(alkylsulfonyl)methylene group, combinations of these, or the like. Specific groups that are used for the fluorinated alcohol group include fluorinated hydroxyalkyl groups, such as a hexafluoroisopropanol group in some embodiments. Specific groups that are used for the carboxylic acid group include acrylic acid groups, methacrylic acid groups, or the like.

In some embodiments, the polymer resin also includes other groups attached to the hydrocarbon structure that help to improve a variety of properties of the polymerizable resin. For example, inclusion of a lactone group to the hydrocarbon structure assists to reduce the amount of line edge roughness (LER) after the photoresist has been developed, thereby helping to reduce the number of defects that occur during development. In some embodiments, the lactone groups include rings having five to seven members, although any suitable lactone structure may alternatively be used for the lactone group.

In some embodiments, the polymer resin includes groups that can assist in increasing the adhesiveness of the photoresist layer 15 to underlying structures (e.g., substrate 10). Polar groups may be used to help increase the adhesiveness. Suitable polar groups include hydroxyl groups, cyano groups, or the like, although any suitable polar group may, alternatively, be used.

Optionally, the polymer resin includes one or more alicyclic hydrocarbon structures that do not also contain a group which will decompose in some embodiments. In some embodiments, the hydrocarbon structure that does not contain a group which will decompose includes structures such as 1-adamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate, cyclohexyl (methacrylate), combinations of these, or the like.

In some embodiments, the amount of polymer resin in the photoresist composition ranges from about 1 wt. % to about 15 wt. % based on the weight of the solvent for the photoresist composition. If the concentration of the polymer resin is less than about 1 wt. % the photoresist coating will be too thin. If the concentration of the polymer resin is greater than about 15 wt. % the photoresist composition is too viscous and it will be difficult to provide a photoresist coating of uniform thickness on the substrate. In some embodiments, the amount of polymer resin in the photoresist composition ranges from about 2 wt. % to about 10 wt. % based on the weight of the solvent. In other embodiments, the amount of polymer resin ranges from about 3 wt. % to about 7 wt. % based on the weight of the solvent.

Additionally, embodiments of the photoresist include one or more photoactive compounds (PACs). The PACs are photoactive components, such as photoacid generators, photobase generators, free-radical generators, or the like. The PACs may be positive-acting or negative-acting. In some embodiments in which the PACs are a photoacid generator, the PACs include halogenated triazines, onium salts, diazonium salts, aromatic diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonate, oxime sulfonate, diazodisulfone, disulfone, o-nitrobenzylsulfonate, sulfonated esters, halogenated sulfonyloxy dicarboximides, diazodisulfones, α-cyanooxyamine-sulfonates, imidesulfonates, ketodiazosulfones, sulfonyldiazoesters, 1,2-di(arylsulfonyl)hydrazines, nitrobenzyl esters, and the s-triazine derivatives, combinations of these, or the like.

Specific examples of photoacid generators include α-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarb-o-ximide (MDT), N-hydroxy-naphthalimide (DDSN), benzoin tosylate, t-butylphenyl-α-(p-toluenesulfonyloxy)-acetate and t-butyl-α-(p-toluenesulfonyloxy)-acetate, triarylsulfonium and diaryliodonium hexafluoroantimonates, hexafluoroarsenates, trifluoromethanesulfonates, iodonium perfluorooctanesulfonate, N-camphorsulfonyloxynaphthalimide, N-pentafluorophenylsulfonyloxynaphthalimide, ionic iodonium sulfonates such as diaryl iodonium (alkyl or aryl)sulfonate and bis-(di-t-butylphenyl)iodonium camphanylsulfonate, perfluoroalkanesulfonates such as perfluoropentanesulfonate, perfluorooctanesulfonate, perfluoromethanesulfonate, aryl (e.g., phenyl or benzyl)triflates such as triphenylsulfonium triflate or bis-(t-butylphenyl)iodonium triflate; pyrogallol derivatives (e.g., trimesylate of pyrogallol), trifluoromethanesulfonate esters of hydroxyimides, α,α′-bis-sulfonyl-diazomethanes, sulfonate esters of nitro-substituted benzyl alcohols, naphthoquinone-4-diazides, alkyl disulfones, or the like.

In some embodiments in which the PACs are free-radical generators, the PACs include n-phenylglycine; aromatic ketones, including benzophenone, N,N′-tetramethyl-4,4′-diaminobenzophenone, N,N′-tetraethyl-4,4′-diaminobenzophenone, 4-methoxy-4′-dimethylaminobenzo-phenone, 3,3′-dimethyl-4-methoxybenzophenone, p,p′-bis(dimethylamino)benzo-phenone, p,p′-bis(diethylamino)-benzophenone; anthraquinone, 2-ethylanthraquinone; naphthaquinone; and phenanthraquinone; benzoins including benzoin, benzoinmethylether, benzoinisopropylether, benzoin-n-butylether, benzoin-phenylether, methylbenzoin and ethylbenzoin; benzyl derivatives, including dibenzyl, benzyldiphenyldisulfide, and benzyldimethylketal; acridine derivatives, including 9-phenylacridine, and 1,7-bis(9-acridinyl)heptane; thioxanthones, including 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, and 2-isopropylthioxanthone; acetophenones, including 1,1-dichloroacetophenone, p-t-butyldichloro-acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 2,2-dichloro-4-phenoxyacetophenone; 2,4,5-triarylimidazole dimers, including 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di-(m-methoxyphenyl imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer, 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer and 2-(p-methylmercaptophenyl)-4,5-diphenylimidazole dimmer; combinations of these, or the like.

In some embodiments in which the PACs are photobase generators, the PACs includes quaternary ammonium dithiocarbamates, α aminoketones, oxime-urethane containing molecules such as dibenzophenoneoxime hexamethylene diurethane, ammonium tetraorganylborate salts, and N-(2-nitrobenzyloxycarbonyl)cyclic amines, combinations of these, or the like.

In some embodiments, the photoresist composition includes about 1 wt. % to about 10 wt. % of a photoactive compound (PAC) based on the weight of the polymer resin. If the concentration of the photoactive compound is less than about 1 wt. % it will not have the desired effect of improving the photosensitivity of the photoresist composition. A concentration of the photoactive compound greater than about 10 wt. % will not provide a significant improvement in photosensitivity over a concentration of about 10 wt. %.

As one of ordinary skill in the art will recognize, the chemical compounds listed herein are merely intended as illustrated examples of the PACs and are not intended to limit the embodiments to only those PACs specifically described. Rather, any suitable PAC may be used, and all such PACs are fully intended to be included within the scope of the present embodiments.

In some embodiments, a cross-linking agent is added to the photoresist. The cross-linking agent reacts with one group from one of the hydrocarbon structures in the polymer resin and also reacts with a second group from a separate one of the hydrocarbon structures in order to cross-link and bond the two hydrocarbon structures together. This bonding and cross-linking increases the molecular weight of the polymer products of the cross-linking reaction and increases the overall linking density of the photoresist. Such an increase in density and linking density helps to improve the resist pattern. In some embodiments, the photoresist composition includes about 1 wt. % to about 20 wt. % of the cross-linking agent based on the weight of the polymer resin. In some embodiments, the photoresist composition includes about 1 wt. % to about 10 wt. % of the cross-linking agent based on the weight of the polymer resin. Concentrations of the cross-linking agent less than about 1 wt. % provide insufficient cross-linking effect. Concentrations of the cross-linking agent greater than about 20 wt. % will not provide any beneficial effect over a concentration of about 20 wt. % cross-linking agent.

In some embodiments the cross-linking agent has the following structure:

wherein C is carbon, n ranges from 1 to 15; A and B independently include a hydrogen atom, a hydroxyl group, a halide, an aromatic carbon ring, or a straight or cyclic alkyl, alkoxyl/fluoro, alkyl/fluoroalkoxyl chain having a carbon number of between 1 and 12, and each carbon C contains A and B; a first terminal carbon C at a first end of a carbon C chain includes X and a second terminal carbon C at a second end of the carbon chain includes Y, wherein X and Y independently include an amine group, a thiol group, a hydroxyl group, an isopropyl alcohol group, or an isopropyl amine group, except when n=1 then X and Y are bonded to the same carbon C. Specific examples of materials that may be used as the cross-linking agent include the following:

Alternatively, instead of or in addition to the cross-linking agent being added to the photoresist composition, a coupling reagent is added in some embodiments, in which the coupling reagent is added in addition to the cross-linking agent. The coupling reagent assists the cross-linking reaction by reacting with the groups on the hydrocarbon structure in the polymer resin before the cross-linking reagent, allowing for a reduction in the reaction energy of the cross-linking reaction and an increase in the rate of reaction. The bonded coupling reagent then reacts with the cross-linking agent, thereby coupling the cross-linking agent to the polymer resin. In some embodiments, the photoresist composition includes about 1 wt. % to about 20 wt. % of the coupling reagent based on the weight of the polymer resin. Concentrations of the coupling reagent less than about 1 wt. % provide insufficient assistance to the cross-linking. Concentrations of the cross-linking agent greater than about 20 wt. % will not provide a significant improvement assistance to cross-linking over a concentration of about 20 wt. %.

Alternatively, in some embodiments in which the coupling reagent is added to the photoresist without the cross-linking agent, the coupling reagent is used to couple one group from one of the hydrocarbon structures in the polymer resin to a second group from a separate one of the hydrocarbon structures in order to cross-link and bond the two polymers together. However, in such an embodiment the coupling reagent, unlike the cross-linking agent, does not remain as part of the polymer, and only assists in bonding one hydrocarbon structure directly to another hydrocarbon structure.

In some embodiments, the coupling reagent has the following structure:

where R is a carbon atom, a nitrogen atom, a sulfur atom, or an oxygen atom; M includes a chlorine atom, a bromine atom, an iodine atom, —NO₂; —SO₃—; —H; —CN; —NCO, —OCN; —CO₂—; —OH; —OR*, —OC(O)CR*; —SR, —SO2N(R*)₂; —SO₂R*; —SOR; —OC(O)R*; —C(O)OR*; —C(O)R*; —Si(OR*)₃; —Si(R*)₃; epoxy groups, or the like; and R* is a substituted or unsubstituted C1-C12 alkyl, C1-C12 aryl, C1-C12 aralkyl, or the like. Specific examples of materials used as the coupling reagent in some embodiments include the following:

In some embodiments, the photoresist includes a protective polymer that forms a protective layer when applied to a layer to be patterned or substrate 10, as described in U.S. application Ser. No. 15/994,615, incorporated herein by reference in its entirety. The protective layer prevents contaminants, including particles, moisture, and ammonia, from being absorbed into or impregnating the photoresist layer 15. In some embodiments, the protective polymer has fluorocarbon pendant groups. In an embodiment, a main chain of the polymer having fluorocarbon pendant groups is a polyhydroxystyrene, a polyacrylate, or a polymer formed from a 1 to 10 carbon monomer. In an embodiment, the polymer having fluorocarbon pendant groups includes from about 0.1 wt. % to about 10 wt. % of one or more polar functional groups selected from the group consisting —OH, —NH₃, —NH₂, and —SO₃ based on the total weight of the polymer having fluorocarbon pendant groups. In an embodiment, the polymer having fluorocarbon pendant groups includes from about 0.1 wt. % to about 10 wt. % of the fluorocarbon pendant groups based on the total weight of the polymer having fluorocarbon pendant groups. Less than about 0.1 wt. % of the fluorocarbon pendant groups does not provide a significant improvement in the protective layer of the photoresist composition. Greater than about 10 wt. % of the fluorocarbon pendants will not provide a significant improvement in the protective layer over a concentration of about 10 wt. %.

In an embodiment, the fluorocarbon pendant groups are attached to a polymer main chain via a linking unit R1 of at least one selected from the group consisting of 1-9 carbon unbranched, branched, cyclic, noncyclic, saturated, or unsaturated hydrocarbon with optional halogen substituents; —S—; —P—; —P(O₂); —C(═O)S—; —C(═O)O—; —O—; —N—; —C(═O)N—; —SO₂O—; —SO₂S—; —SO—; —SO₂—; and —C(═O)—. In an embodiment, the fluorocarbon pendant group is selected from the group consisting of C_(x)F_(y), where 1≤x≤9 and 3≤y≤12; and —(C(CF₃)₂OH)—. Examples of C_(x)F_(y) units attached to the polymer chain via a linking unit R1 according to embodiments of the disclosure are shown in FIG. 7. As shown, in some embodiments, C_(x)F_(y) is one or more selected from the group consisting of —C₂F₅, —CH₂CH₂C₃F₇, —(C(CF₃)₂OH), —C(═O)OC₄F₉, —CH₂OC₄F₉, and —C(═O)O(C(CF₃)₂OH).

In some embodiments, the amount of protective polymer having fluorocarbon pendant groups in the photoresist/protective polymer mixture ranges from about 1 wt. % to about 10 wt. % based on the total weight of the photoresist/protective polymer mixture. In some embodiments, the protective polymer having fluorocarbon pendant groups has a weight average molecular weight of about 3000 to about 15,000. In some embodiments, the protective polymer having fluorocarbon pendant groups has a weight average molecular weight of about 6000 to about 11,000. In some embodiments, the protective layer has a thickness ranging from about 0.1 nm to about 20 nm. In some embodiments, the thickness of the protective layer ranges from about 1 nm to about 15 nm. In some embodiments, the contact angle of the protective layer to water is greater than 75°.

The individual components of the photoresist are placed into a solvent in order to aid in the mixing and dispensing of the photoresist. To aid in the mixing and dispensing of the photoresist, the solvent is chosen at least in part based upon the materials chosen for the polymer resins as well as the PACs. In some embodiments, the solvent is chosen such that the polymer resins and the PACs can be evenly dissolved into the solvent and dispensed upon the layer to be patterned.

In some embodiments, the solvent is an organic solvent, and includes one or more of any suitable solvent such as ketones, alcohols, polyalcohols, ethers, glycol ethers, cyclic ethers, aromatic hydrocarbons, esters, propionates, lactates, lactic esters, alkylene glycol monoalkyl ethers, alkyl lactates, alkyl alkoxypropionates, cyclic lactones, monoketone compounds that contain a ring, alkylene carbonates, alkyl alkoxyacetate, alkyl pyruvates, lactate esters, ethylene glycol alkyl ether acetates, diethylene glycols, propylene glycol alkyl ether acetates, alkylene glycol alkyl ether esters, alkylene glycol monoalkyl esters, or the like.

Specific examples of materials that may be used as the solvent for the photoresist include, acetone, methanol, ethanol, toluene, xylene, 4-hydroxy-4-methyl-2-pentatone, tetrahydrofuran, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, ethylene glycol dimethyl ether, ethylene glycol dimethyl ether, ethylene glycol methylethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol, diethylene glycol monoacetate, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethylmethyl ether, diethethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-2-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, propylene glycol, propylene glycol monoacetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monopropyl methyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol monomethyl ether propionate, propylene glycol monoethyl ether propionate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethyl 3-ethoxypropionate, methyl 3-methoxypropionate, methyl 3-ethoxypropionate, and ethyl 3-methoxypropionate, β-propiolactone, β-butyrolactone, γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-octanoic lactone, α-hydroxy-γ-butyrolactone, 2-butanone, 3-methylbutanone, pinacolone, 2-pentanone, 3-pentanone, 4-methyl-2-pentanone, 2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone, 2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone, 3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone, 2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone, 3-decanone, 4-decanone, 5-hexene-2-one, 3-pentene-2-one, cyclopentanone, 2-methylcyclopentanone, 3-methylcyclopentanone, 2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone, cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, 4-ethylcyclohexanone, 2,2-dimethylcyclohexanone, 2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone, 2-methylcycloheptanone, 3-methylcycloheptanone, propylene carbonate, vinylene carbonate, ethylene carbonate, butylene carbonate, acetate-2-methoxyethyl, acetate-2-ethoxyethyl, acetate-2-(2-ethoxyethoxy)ethyl, acetate-3-methoxy-3-methylbutyl, acetate-1-methoxy-2-propyl, dipropylene glycol, monomethylether, monoethylether, monopropylether, monobutylether, monophenylether, dipropylene glycol monoacetate, dioxane, methyl pyruvate, ethyl pyruvate, propyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, n-methylpyrrolidone (NMP), 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether, propylene glycol monomethyl ether, methyl propionate, ethyl propionate, ethyl ethoxy propionate, methylethyl ketone, cyclohexanone, 2-heptanone, cyclopentanone, cyclohexanone, ethyl 3-ethoxypropionate, propylene glycol methyl ether acetate (PGMEA), methylene cellosolve, 2-ethoxyethanol, N-methylformamide, N,N-dimethylformamide, N-methylformanilide, N-methylacetamide, N,N-dimethylacetamide, dimethylsulfoxide, benzyl ethyl ether, dihexyl ether, acetonylacetone, isophorone, caproic acid, caprylic acid, 1-octanol, 1-nonanol, benzyl alcohol, benzyl acetate, ethyl benzoate, diethyl oxalate, diethyl maleate, phenyl cellosolve acetate, or the like.

In some embodiments, the solvent is selected from the group consisting of dimethylsulfoxide, acetone, ethylene glycol, methanol, ethanol, propanol, isopropanol, propanediol, water, 4-methyl-2-pentanone, hydrogen peroxide, butyldiglycol, and combinations thereof.

As one of ordinary skill in the art will recognize, the materials listed and described above as examples of materials that may be used for the solvent component of the photoresist are merely illustrative and are not intended to limit the embodiments. Rather, any suitable materials that dissolve the polymer resin and the PACs may be used to help mix and apply the photoresist. All such materials are fully intended to be included within the scope of the embodiments.

Additionally, while individual ones of the above described materials may be used as the solvent for the photoresist and protective polymer, in other embodiments more than one of the above described materials are used. For example, in some embodiments, the solvent includes a combination mixture of two or more of the materials described. All such combinations are fully intended to be included within the scope of the embodiments.

In addition to the polymer resins, the PACs, the solvents, the cross-linking agent, and the coupling reagent, some embodiments of the photoresist also include a number of other additives that assist the photoresist to obtain high resolution. For example, some embodiments of the photoresist also include surfactants in order to help improve the ability of the photoresist to coat the surface on which it is applied. In some embodiments, the surfactants include nonionic surfactants, polymers having fluorinated aliphatic groups, surfactants that contain at least one fluorine atom and/or at least one silicon atom, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

Specific examples of materials used as surfactants in some embodiments include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenol ether, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitan tristearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, polyethylene glycol distearate, polyethylene glycol dilaurate, polyethylene glycol dilaurate, polyethylene glycol, polypropylene glycol, polyoxyethylenestearyl ether, polyoxyethylene cetyl ether, fluorine containing cationic surfactants, fluorine containing nonionic surfactants, fluorine containing anionic surfactants, cationic surfactants and anionic surfactants, polyethylene glycol, polypropylene glycol, polyoxyethylene cetyl ether, combinations thereof, or the like. In some embodiments, the photoresist composition contains from about 0.001 wt. % to about 1 wt. % of the surfactant based on the total weight of the photoresist composition.

Another additive in some embodiments of the photoresist is a dissolution inhibitor to help control dissolution of the photoresist during development. In an embodiment bile-salt esters may be utilized as the dissolution inhibitor. Specific examples of dissolution inhibitors in some embodiments include cholic acid, deoxycholic acid, lithocholic acid, t-butyl deoxycholate, t-butyl lithocholate, and t-butyl-3-acetyl lithocholate. In some embodiments, the photoresist composition contains from about 0.001 wt. % to about 1 wt. % of the dissolution inhibitor based on the total weight of the photoresist composition.

Another additive in some embodiments of the photoresist is a plasticizer. Plasticizers may be used to reduce delamination and cracking between the photoresist and underlying layers (e.g., the layer to be patterned). Plasticizers include monomeric, oligomeric, and polymeric plasticizers, such as oligo- and polyethyleneglycol ethers, cycloaliphatic esters, and non-acid reactive steroidaly-derived materials. Specific examples of materials used for the plasticizer in some embodiments include dioctyl phthalate, didodecyl phthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, triacetyl glycerine, or the like. In some embodiments, the photoresist composition contains from about 0.001 wt. % to about 1 wt. % of the plasticizer based on the total weight of the photoresist composition.

A coloring agent is another additive included in some embodiments of the photoresist. The coloring agent observers examine the photoresist and find any defects that may need to be remedied prior to further processing. In some embodiments, the coloring agent is a triarylmethane dye or a fine particle organic pigment. Specific examples of materials in some embodiments include crystal violet, methyl violet, ethyl violet, oil blue #603, Victoria Pure Blue BOH, malachite green, diamond green, phthalocyanine pigments, azo pigments, carbon black, titanium oxide, brilliant green dye (C. I. 42020), Victoria Pure Blue FGA (Linebrow), Victoria BO (Linebrow) (C. I. 42595), Victoria Blue BO (C. I. 44045), rhodamine 6G (C. I. 45160), benzophenone compounds, such as 2,4-dihydroxybenzophenone and 2,2′,4,4′-tetrahydroxybenzophenone; salicylic acid compounds, such as phenyl salicylate and 4-t-butylphenyl salicylate; phenylacrylate compounds, such as ethyl-2-cyano-3,3-diphenylacrylate, and 2′-ethylhexyl-2-cyano-3,3-diphenylacrylate; benzotriazole compounds, such as 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, and 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole; coumarin compounds, such as 4-methyl-7-diethylamino-1-benzopyran-2-one; thioxanthone compounds, such as diethylthioxanthone; stilbene compounds, naphthalic acid compounds, azo dyes, phthalocyanine blue, phthalocyanine green, iodine green, Victoria blue, crystal violet, titanium oxide, naphthalene black, Photopia methyl violet, bromphenol blue and bromcresol green; laser dyes, such as Rhodamine G6, Coumarin 500, DCM (4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H pyran)), Kiton Red 620, Pyrromethene 580, or the like. Additionally, one or more coloring agents may be used in combination to provide the desired coloring. In some embodiments, the photoresist composition contains from about 0.001 wt. % to about 1 wt. % of the coloring agent based on the total weight of the photoresist composition.

Adhesion additives are added to some embodiments of the photoresist to promote adhesion between the photoresist and an underlying layer upon which the photoresist has been applied (e.g., the layer to be patterned). In some embodiments, the adhesion additives include a silane compound with at least one reactive substituent such as a carboxyl group, a methacryloyl group, an isocyanate group and/or an epoxy group. Specific examples of the adhesion components include trimethoxysilyl benzoic acid, γ-methacryloxypropyl trimethoxy silane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyl triethoxy silane, γ-glycidoxypropyl trimethoxy silane, β-(3,4-epoxycyclohexyl)ethyl trimethoxy silane, benzimidazoles and polybenzimidazoles, a lower hydroxyalkyl substituted pyridine derivative, a nitrogen heterocyclic compound, urea, thiourea, an organophosphorus compound, 8-oxyquinoline, 4-hydroxypteridine and derivatives, 1,10-phenanthroline and derivatives, 2,2′-bipyridine and derivatives, benzotriazoles, organophosphorus compounds, phenylenediamine compounds, 2-amino-1-phenylethanol, N-phenylethanolamine, N-ethyldiethanolamine, N-ethylethanolamine and derivatives, benzothiazole, and a benzothiazoleamine salt having a cyclohexyl ring and a morpholine ring, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyl trimethoxysilane, combinations thereof, or the like. In some embodiments, the photoresist composition contains from about 0.001 wt. % to about 1 wt. % of the adhesion additive based on the total weight of the photoresist composition.

Surface leveling agents are added to some embodiments of the photoresist to assist a top surface of the photoresist to be level, so that impinging light will not be adversely modified by an unlevel surface. In some embodiments, surface leveling agents include fluoroaliphatic esters, hydroxyl terminated fluorinated polyethers, fluorinated ethylene glycol polymers, silicones, acrylic polymer leveling agents, combinations thereof, or the like. In some embodiments, the photoresist composition contains from about 0.001 wt. % to about 1 wt. % of the surface leveling agents based on the total weight of the photoresist composition.

Some embodiments of the photoresist include metal oxide nanoparticles. The metal oxide nanoparticles improve actinic radiation absorption in some embodiments. In some embodiments, the photoresist includes one or more metal oxides nanoparticles selected from the group consisting of titanium dioxide, zinc oxide, zirconium dioxide, nickel oxide, cobalt oxide, manganese oxide, copper oxides, iron oxides, strontium titanate, tungsten oxides, vanadium oxides, chromium oxides, tin oxides, hafnium oxide, indium oxide, cadmium oxide, molybdenum oxide, tantalum oxides, niobium oxide, aluminum oxide, and combinations thereof. As used herein, nanoparticles are particles having an average particle size between about 1 nm and about 20 nm. Metal oxide nanoparticle sizes less than about 1 nm are difficult to obtain and use in photoresist compositions. Metal oxide nanoparticles greater than about 20 nm are too large for use in a resist in embodiments of the disclosure. In some embodiments the metal oxide nanoparticles have an average particle size between about 2 and about 5 nm. In some embodiments, the amount of metal oxide nanoparticles in the photoresist composition ranges from about 1 wt. % to about 15 wt. % based on the weight of the solvent for the photoresist composition. In some embodiments, the amount of nanoparticles in the photoresist composition ranges from about 2 wt. % to about 10 wt. % based on the weight of the solvent for the photoresist composition. Concentrations of the metal oxide nanoparticles less than about 1 wt. % provide a photoresist coating that is too thin. Concentrations of the metal oxide nanoparticles greater than about 15 wt. % will provide a photoresist composition that is too viscous and that will be difficult to provide a photoresist coating of uniform thickness on the substrate.

In some embodiments, the metal oxide nanoparticles are complexed with a ligand. In some embodiments, the ligand is a carboxylic acid or sulfonic acid ligand. For example, in some embodiments, zirconium oxide or hafnium oxide nanoparticles are complexed with methacrylic acid forming hafnium methacrylic acid (HfMAA) or zirconium methacrylic acid (ZrMAA). In some embodiments, the metal oxide nanoparticles are complexed with ligands including aliphatic or aromatic groups. The aliphatic or aromatic groups may be unbranched or branched with cyclic or noncyclic saturated pendant groups containing 1-9 carbons, including alkyl groups, alkenyl groups, and phenyl groups. The branched groups may be further substituted with oxygen or halogen. In some embodiments, the ligand concentration is about 10 wt. % to about 40 wt. % based on the weight on the metal oxide nanoparticles. At concentrations of the ligand below about 10 wt. % the concentration of the ligand is insufficient to complex the metal oxide nanoparticles. Concentrations of the ligand above about 40 wt. % do not provide a significant improvement in complexing the metal oxide nanoparticles over concentrations of the ligand at about 40 wt. %.

In some embodiments, the metal oxide/ligand complexes are formed of a cluster including metallic core having a metal with high EUV absorption, such as Cs, Ba, La, Ce, In, Sn, Ag, or Sb combined with oxygen and/or nitrogen to form 1 to 12 metal core-clusters. The metallic core-clusters are complexed with ligands including aliphatic or aromatic groups. The aliphatic or aromatic groups may be unbranched or branched with cyclic or noncyclic saturated pendant groups containing 1-9 carbons, including alkyl groups, alkenyl groups, and phenyl groups. The branched groups may be further substituted with oxygen or halogen in some embodiments.

Examples of suitable metal oxide/ligand complexes according to embodiments of the disclosure are:

In some embodiments, the ligand is HfMAA or ZrMAA dissolved at about a 5 wt. % to about 10 wt. % weight range in a coating solvent, such as propylene glycol methyl ether acetate (PGMEA).

In some embodiments, an acid having an acid dissociation constant, pKa, of −15<pKa<4, or a base having a pKa of 40>pKa>9 is included in the photoresist composition as a ligand stabilizer to stabilize the ligand. The ligand stabilizer inhibits the ligand from separating from the metal/ligand complex. The ligand stabilizer maintains a uniform concentration of metal oxide nanoparticles in the photoresist composition.

The acid dissociation constant, pK_(a), is the logarithmic constant of the acid dissociation constant K_(a). K_(a) is a quantitative measure of the strength of an acid in solution. K_(a) is the equilibrium constant for the dissociation of a generic acid according to the equation HA+H₂O↔A⁻+H₃O⁺, where HA dissociates into its conjugate base, A⁻, and a hydrogen ion which combines with a water molecule to form a hydronium ion. The dissociation constant can be expressed as a ratio of the equilibrium concentrations:

$K_{a} = {\frac{\left\lbrack A^{-} \right\rbrack\left\lbrack {H_{3}O^{+}} \right\rbrack}{\lbrack{HA}\rbrack\left\lbrack {H_{2}O} \right\rbrack}.}$ In most cases, the amount of water is constant and the equation can be simplified to HAχA⁻+H⁺, and

$K_{a} = {\frac{\left\lbrack A^{-} \right\rbrack\left\lbrack H^{+} \right\rbrack}{\lbrack{HA}\rbrack}.}$ The logarithmic constant, pK_(a) is related to K_(a) by the equation pK_(a)=−log₁₀(K_(a)). The lower the value of pK_(a) the stronger the acid. Conversely, the higher the value of pK_(a) the stronger the base. In some embodiments, the amount of the acid or base ranges from about 0.001 wt. % to about 20 wt. % based on the total weight of the photoresist composition. In some embodiments, the amount of acid or base ranges from about 0.1 wt. % to about 15 wt. % based on the total weight of the photoresist composition. In some embodiments, the amount of acid or base ranges from about 1 wt. % to about 10 wt. % based on the total weight of the photoresist composition.

In some embodiments, the ligand stabilizer is an acid selected from the group consisting of ethanedioic acid (oxalic acid), methanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid, uric acid, trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonic acid, methanesulfonic acid, maleic acid, carbonic acid, HNO₃, H₂SO₄, HCl, oxoethanoic acid, 2-hydroxyethanoic acid, propanedioic acid, butanedioic acid, 3-oxobutanoic acid, hydroxylamine-O-sulfonic acid, formamidine sulfinic acid, methylsulfamic acid, sulfoacetic acid, 1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid, nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid, and combinations thereof. In some embodiments, the ligand stabilizer is a base selected from the group consisting of monoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol, 1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene, tetrabutylammonium hydroxide, tetramethylammonium hydroxide, ammonium hydroxide, ammonium sulfamate, ammonium carbamate, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and combinations thereof.

In some embodiments, the polymer resins and the PACs, along with any desired additives or other agents, are added to the solvent for application. Once added, the mixture is then mixed in order to achieve a homogenous composition throughout the photoresist to ensure that there are no defects caused by uneven mixing or nonhomogeneous composition of the photoresist. Once mixed together, the photoresist may either be stored prior to its usage or used immediately.

Once ready, the photoresist is applied onto the layer to be patterned, as shown in FIG. 2, such as the substrate 10 to form a photoresist layer 15. In some embodiments, the photoresist is applied using a process such as a spin-on coating process, a dip coating method, an air-knife coating method, a curtain coating method, a wire-bar coating method, a gravure coating method, a lamination method, an extrusion coating method, combinations of these, or the like. In some embodiments, the photoresist layer 15 thickness ranges from about 10 nm to about 300 nm.

After the photoresist layer 15 has been applied to the substrate 10, a pre-bake of the photoresist layer is performed in some embodiments to cure and dry the photoresist prior to radiation exposure (see FIG. 1). The curing and drying of the photoresist layer 15 removes the solvent component while leaving behind the polymer resin, the PACs, the cross-linking agent, and the other chosen additives. In some embodiments, the pre-baking is performed at a temperature suitable to evaporate the solvent, such as between about 50° C. and 250° C., although the precise temperature depends upon the materials chosen for the photoresist. The pre-baking is performed for a time sufficient to cure and dry the photoresist layer, such as between about 10 seconds to about 10 minutes.

FIG. 3 illustrates a selective exposure of the photoresist layer to form an exposed region 50 and an unexposed region 15. In some embodiments, the exposure to radiation is carried out by placing the photoresist coated substrate in a photolithography tool. The photolithography tool includes a photomask 30, optics, an exposure radiation source to provide the radiation 45 for exposure, and a movable stage for supporting and moving the substrate under the exposure radiation.

In some embodiments, the radiation source (not shown) supplies radiation 45, such as ultraviolet light, to the photoresist layer 15 in order to induce a reaction of the PACs, which in turn reacts with the polymer resin to chemically alter those regions of the photoresist layer to which the radiation 45 impinges. In some embodiments, the radiation is electromagnetic radiation, such as g-line (wavelength of about 436 nm), i-line (wavelength of about 365 nm), ultraviolet radiation, far ultraviolet radiation, extreme ultraviolet, electron beams, or the like. In some embodiments, the radiation source is selected from the group consisting of a mercury vapor lamp, xenon lamp, carbon arc lamp, a KrF excimer laser light (wavelength of 248 nm), an ArF excimer laser light (wavelength of 193 nm), an F₂ excimer laser light (wavelength of 157 nm), or a CO₂ laser-excited Sn plasma (extreme ultraviolet, wavelength of 13.5 nm).

In some embodiments, optics (not shown) are used in the photolithography tool to expand, reflect, or otherwise control the radiation before or after the radiation 45 is patterned by the photomask 30. In some embodiments the optics include one or more lenses, mirrors, filters, and combinations thereof to control the radiation 45 along its path.

In an embodiment, the patterned radiation 45 is extreme ultraviolet light having a 13.5 nm wavelength, the PAC is a photoacid generator, the group to be decomposed is a carboxylic acid group on the hydrocarbon structure, and a cross linking agent is used. The patterned radiation 45 impinges upon the photoacid generator, the photoacid generator absorbs the impinging patterned radiation 45. This absorption initiates the photoacid generator to generate a proton (e.g., a H⁺ atom) within the photoresist layer 15. When the proton impacts the carboxylic acid group on the hydrocarbon structure, the proton reacts with the carboxylic acid group, chemically altering the carboxylic acid group and altering the properties of the polymer resin in general. The carboxylic acid group then reacts with the cross-linking agent to cross-link with other polymer resins within the exposed region of the photoresist layer 15.

In some embodiments, the exposure of the photoresist layer 15 uses an immersion lithography technique. In such a technique, an immersion medium (not shown) is placed between the final optics and the photoresist layer, and the exposure radiation 45 passes through the immersion medium.

After the photoresist layer 15 has been exposed to the exposure radiation 45, a post-exposure baking is performed in some embodiments to assist in the generating, dispersing, and reacting of the acid/base/free radical generated from the impingement of the radiation 45 upon the PACs during the exposure. Such thermal assistance helps to create or enhance chemical reactions which generate chemical differences between the exposed region 50 and the unexposed region 52 within the photoresist layer 15. These chemical differences also cause differences in the solubility between the exposed region 50 and the unexposed region 52. In some embodiments, the post-exposure baking occurs at temperatures ranging from about 50° C. to about 160° C. for a period of between about 20 seconds and about 120 seconds.

The inclusion of the cross-linking agent into the chemical reactions helps the components of the polymer resin (e.g., the individual polymers) react and bond with each other, increasing the molecular weight of the bonded polymer in some embodiments. In particular, an initial polymer has a side chain with a carboxylic acid protected by one of the groups to be removed/acid labile groups. The groups to be removed are removed in a de-protecting reaction, which is initiated by a proton H⁺ generated by, e.g., the photoacid generator during either the exposure process or during the post-exposure baking process. The H⁺ first removes the groups to be removed/acid labile groups and another hydrogen atom may replace the removed structure to form a de-protected polymer. Once de-protected, a cross-linking reaction occurs between two separate de-protected polymers that have undergone the de-protecting reaction and the cross-linking agent in a cross-linking reaction. In particular, hydrogen atoms within the carboxylic groups formed by the de-protecting reaction are removed and the oxygen atoms react with and bond with the cross-linking agent. This bonding of the cross-linking agent to two polymers bonds the two polymers not only to the cross-linking agent but also bonds the two polymers to each other through the cross-linking agent, thereby forming a cross-linked polymer.

By increasing the molecular weight of the polymers through the cross-linking reaction, the new cross-linked polymer becomes less soluble in conventional organic solvent negative resist developers.

Development is performed using a solvent. In some embodiments where positive tone development is desired, a positive tone developer such as a basic aqueous solution is used to remove regions 50 of the photoresist exposed to radiation. In some embodiments, the positive tone developer 57 includes one or more selected from tetramethylammonium hydroxide (TMAH), tetrabutylammonium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium silicate, sodium metasilicate, aqueous ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, monoethanolamine, diethanolamine, triethanolamine, dimethylaminoethanol, diethylaminoethanol, ammonia, caustic soda, caustic potash, sodium metasilicate, potassium metasilicate, sodium carbonate, tetraethylammonium hydroxide, combinations of these, or the like.

In some embodiments where negative tone development is desired, an organic solvent or critical fluid is used to remove the unexposed regions 52 of the photoresist. In some embodiments, the negative tone developer 57 includes one or more selected from hexane, heptane, octane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, and like hydrocarbon solvents; critical carbon dioxide, methanol, ethanol, propanol, butanol, and like alcohol solvents; diethyl ether, dipropyl ether, dibutyl ether, ethyl vinyl ether, dioxane, propylene oxide, tetrahydrofuran, cellosolve, methyl cellosolve, butyl cellosolve, methyl carbitol, diethylene glycol monoethyl ether and like ether solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone and like ketone solvents; methyl acetate, ethyl acetate, propyl acetate, butyl acetate and like ester solvents; pyridine, formamide, and N,N-dimethyl formamide or the like.

In some embodiments, the developer 57 is applied to the protective layer and photoresist layer 15 using a spin-on process. In the spin-on process, the developer 57 is applied to the photoresist layer 15 by a dispenser 62 from above while the coated substrate is rotated, as shown in FIG. 4. In the case of a positive resist, the exposed region 50 of the photoresist layer is removed, and in the case of a negative resist the unexposed regions 52 of the photoresist layer are removed. In some embodiments the developer 57 is supplied at a rate of between about 5 ml/min and about 800 ml/min, while the coated substrate 10 is rotated at a speed of between about 100 rpm and about 2000 rpm. In some embodiments, the developer is at a temperature of between about 10° C. and about 80° C. The development operation continues for between about 30 seconds to about 10 minutes in some embodiments.

While the spin-on operation is one suitable method for developing the photoresist layer 15 after exposure, it is intended to be illustrative and is not intended to limit the embodiment. Rather, any suitable development operations, including dip processes, puddle processes, and spray-on methods, may alternatively be used. All such development operations are included within the scope of the embodiments.

In some embodiments, the photoresist developers 57 dissolve the cross-linked, radiation-exposed portions 50 of the photoresist layer 15.

In some embodiments, the photoresist developer 57 includes a major solvent, an acid or a base, and a chelate, as described in U.S. application Ser. No. 15/938,599, incorporated by reference in its entirety. In some embodiments, the concentration of the major solvent is from about 60 wt. % to about 99 wt. % based on the total weight of the photoresist developer. The acid or base concentration is from about 0.001 wt. % to about 20 wt. % based on the total weight of the photoresist developer. In certain embodiments, the acid or base concentration in the developer is from about 0.01 wt. % to about 15 wt. % based on the total weight of the photoresist developer. The chelate concentration is from about 0.001 wt. % to about 20 wt. % of the total weight of the photoresist developer. In certain embodiments, the concentration of the chelate ranges from about 0.01 wt. % to about 15 wt. % based on the total weight of the photoresist developer.

In some embodiments, the major solvent has Hansen solubility parameters of 15<δ_(d)<25, 10<δ_(p)<25, and 6<δ_(h)<30. The units of the Hansen solubility parameters are (Joules/cm³)^(1/2) or, equivalently, MPa^(1/2) and are based on the idea that one molecule is defined as being like another if it bonds to itself in a similar way. δ_(d) is the energy from dispersion forces between molecules. δ_(p) is the energy from dipolar intermolecular force between the molecules. δ_(h) is the energy from hydrogen bonds between molecules. The three parameters, δ_(d), δ_(p), and δ_(h), can be considered as coordinates for a point in three dimensions, known as the Hansen space. The nearer two molecules are in Hansen space, the more likely they are to dissolve into each other.

Solvents having the desired Hansen solubility parameters include dimethyl sulfoxide, acetone, ethylene glycol, methanol, ethanol, propanol, propanediol, water, 4-methyl-2-pentanone, hydrogen peroxide, isopropanol, and butyldiglycol.

In some embodiments, suitable acids for the photoresist developer 57 include an organic acid selected from the group consisting of ethanedioic acid, methanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid, uric acid, trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonic acid, methanesulfonic acid, oxalic acid, maleic acid, carbonic acid, oxoethanoic acid, 2-hydroxyethanoic acid, propanedioic acid, butanedioic acid, 3-oxobutanoic acid, hydroxylamine-o-sulfonic acid, formamidine sulfinic acid, methylsulfamic acid, sulfoacetic acid, 1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid, nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid, and combinations thereof. In some embodiments, the acid is an inorganic acid selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and combinations thereof.

In some embodiments, suitable bases for the photoresist developer 57 include an organic base selected from the group consisting of monoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol, 1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene, tetrabutyl ammonium hydroxide, tetramethylammonium hydroxide, ammonium hydroxide, ammonium sulfamate, ammonium carbamate, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and combinations thereof.

In some embodiments, the chelate is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), ethylenediamine-N,N′-disuccinic acid (EDDS), diethylenetriaminepentaacetic acid (DTPA), polyaspartic acid, trans-1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid monohydrate, ethylenediamine, and combinations thereof, or the like.

In an embodiment, the photoresist developer 57 includes an additional solvent. In some embodiments, the additional solvent includes water; hexane, heptane, octane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, and like hydrocarbon solvents; critical carbon dioxide, methanol, ethanol, propanol, butanol, and like alcohol solvents; diethyl ether, dipropyl ether, dibutyl ether, ethyl vinyl ether, dioxane, propylene oxide, tetrahydrofuran, cellosolve, methyl cellosolve, butyl cellosolve, methyl carbitol, diethylene glycol monoethyl ether and like ether solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone and like ketone solvents; methyl acetate, ethyl acetate, propyl acetate, butyl acetate and like ester solvents; pyridine, formamide, and N,N-dimethyl formamide or the like. In an embodiment, the concentration of the additional solvent is from about 1 wt. % to about 40 wt. % based on the total weight of the developer.

In some embodiments, the photoresist developer 57 includes hydrogen peroxide in a concentration of up to about 10 wt. % based on the total weight of the developer.

In some embodiments, the photoresist developer 57 includes up to about 1 wt. % of a surfactant to increase the solubility and reduce the surface tension on the substrate. In some embodiments, the surfactant is selected from the group consisting of alkylbenzenesulfonates, lignin sulfonates, fatty alcohol ethoxylates, and alkylphenol ethoxylates. In some embodiments, the surfactant is selected from the group consisting of sodium stearate, 4-(5-dodecyl) benzenesulfonate, ammonium lauryl sulfate, sodium lauryl sulfate, sodium laureth sulfate, sodium myreth sulfate, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate, perfluorobutanesulfonate, alkyl-aryl ether phosphate, alkyl ether phosphates, sodium lauroyl sarcosinate, perfluoronononanoate, perfluorooctanoate, octenidine dihydrochloride, cetrimonium bromide, cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride, dimethyldioctadecylammonium chloride, dioctadecyldimethylammonium bromide, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, cocamidopropyl hydroxysultaine, cocamidopropyl betaine, phospholipidsphosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, sphingomyelins, octaethylene glycol monodecyl ether, pentaethylene glycol monodecyl ether, polyethoxylated tallow amine, cocamide monoethanolamine, cocamide diethanolamine, glycerol monostearate, glycerol monolaurate, sorbitan monolaurate, sorbitan monostearate, sorbitan tristearate, and combinations thereof.

During the development process, the developer 57 dissolves the radiation exposed regions 50 of the cross-linked negative resist, exposing the surface of the substrate 10, as shown in FIG. 5, and leaving behind well-defined unexposed photoresist regions 52, having improved definition than provided by conventional negative photoresist photolithography.

After the developing operation S150, remaining developer is removed from the patterned photoresist covered substrate. The remaining developer is removed using a spin-dry process in some embodiments, although any suitable removal technique may be used. After the photoresist layer 15 is developed, and the remaining developer is removed, additional processing is performed while the patterned photoresist layer 52 is in place. For example, an etching operation, using dry or wet etching, is performed in some embodiments, to transfer the pattern of the photoresist layer 52 to the underlying substrate 10, forming recesses 55′ as shown in FIG. 6. The substrate 10 has a different etch resistance than the photoresist layer 15. In some embodiments, the etchant is more selective to the substrate 10 than the photoresist layer 15.

In some embodiments, the substrate 10 and the photoresist layer 15 contain at least one etching resistance molecule. In some embodiments, the etching resistant molecule includes a molecule having a low Onishi number structure, a double bond, a triple bond, silicon, silicon nitride, titanium, titanium nitride, aluminum, aluminum oxide, silicon oxynitride, combinations thereof, or the like.

In some embodiments, a layer to be patterned 60 is disposed over the substrate prior to forming the photoresist layer, as shown in FIG. 8. In some embodiments, the layer to be patterned 60 is a metallization layer or a dielectric layer, such as a passivation layer, disposed over a metallization layer. In embodiments where the layer to be patterned 60 is a metallization layer, the layer to be patterned 60 is formed of a conductive material using metallization processes, and metal deposition techniques, including chemical vapor deposition, atomic layer deposition, and physical vapor deposition (sputtering). Likewise, if the layer to be patterned 60 is a dielectric layer, the layer to be patterned 60 is formed by dielectric layer formation techniques, including thermal oxidation, chemical vapor deposition, atomic layer deposition, and physical vapor deposition.

The photoresist layer 50 is subsequently selectively exposed to actinic radiation 45 to form exposed regions 50 and unexposed regions 52 in the photoresist layer, as shown in FIG. 9, and described herein in relation to FIG. 3. As explained herein the photoresist is a negative photoresist, wherein polymer crosslinking occurs in the exposed regions 50 in some embodiments.

As shown in FIG. 10, the exposed photoresist regions 50 are developed by dispensing developer 57 from a dispenser 62 to form a pattern of photoresist openings 55, as shown in FIG. 11. The development operation is similar to that explained with reference to FIGS. 4 and 5, herein.

Then as shown in FIG. 12, the pattern 55 in the photoresist layer 15 is transferred to the layer to be patterned 60 using an etching operation and the photoresist layer is removed, as explained with reference to FIG. 6 to form pattern 55″ in the layer to be patterned 60.

In some embodiments, the selective exposure of the photoresist layer 15 to form exposed regions 50 and unexposed regions 52 is performed using extreme ultraviolet lithography. In an extreme ultraviolet lithography operation a reflective photomask 65 is used to form the patterned exposure light, as shown in FIG. 13. The reflective photomask 65 includes a low thermal expansion glass substrate 70, on which a reflective multilayer 75 of Si and Mo is formed. A capping layer 80 and absorber layer 85 are formed on the reflective multilayer 75. A rear conductive layer 90 is formed on the back side of the low thermal expansion substrate 70. In extreme ultraviolet lithography, extreme ultraviolet radiation 95 is directed towards the reflective photomask 65 at an incident angle of about 6°. A portion 97 of the extreme ultraviolet radiation is reflected by the Si/Mo multilayer 75 towards the photoresist coated substrate 10, while the portion of the extreme ultraviolet radiation incident upon the absorber 85 is absorbed by the photomask. In some embodiments, additional optics, including mirrors are between the reflective photomask 65 and the photoresist coated substrate.

The novel photoresist composition and photolithography techniques according to the present disclosure provide improved critical dimension variation, smoother photoresist profile, and reduced defects. Photoresist compositions and photolithography techniques according to the present disclosure inhibit photoresist aging. The shelf life of photoresist compositions according to the present disclosure can have a greater than 50% longer shelf life than other photoresist compositions. In some embodiments, the shelf life of the photoresist composition is increased by 100%. In some embodiments, the shelf life of the photoresist increases from 2 weeks to 4 weeks. Use of the disclosed photoresist composition can reduce semiconductor processing costs, as photoresist waste is reduced.

An embodiment of the disclosure is a photoresist composition including a photoresist material including metal oxide nanoparticles and a ligand, and an acid having an acid dissociation constant, pKa, of −15<pKa<4, or a base having a pKa of 40>pKa>9. In an embodiment, the amount of the acid or base ranges from 0.001 wt. % to 20 wt. % based on the total weight of the photoresist composition. In an embodiment, the amount of metal oxide nanoparticles ranges from 1 wt. % to 10 wt. % based on the total weight of the photoresist composition. In an embodiment, the metal oxide nanoparticles have an average particle size ranging from 1 nm to 10 nm. In an embodiment, the metal oxide nanoparticles are selected from the group consisting of titanium dioxide, zinc oxide, zirconium dioxide, nickel oxide, cobalt oxide, manganese oxide, copper oxides, iron oxides, strontium titanate, tungsten oxides, vanadium oxides, chromium oxides, tin oxides, hafnium oxide, indium oxide, cadmium oxide, molybdenum oxide, tantalum oxides, niobium oxide, aluminum oxide, and combinations thereof. In an embodiment, the ligand is a carboxylic acid or sulfonic acid ligand. In an embodiment, the photoresist includes a polymer resin and a photoactive compound.

Another embodiment of the disclosure is a photoresist composition including a photoresist material including metal oxide nanoparticles and a ligand, and a ligand stabilizer. In an embodiment, the ligand stabilizer is selected from the group consisting of ethanedioic acid, methanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid, uric acid, trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonic acid, methanesulfonic acid, oxalic acid, maleic acid, carbonic acid, HNO₃, H₂SO₄, HCl, oxoethanoic acid, 2-hydroxyethanoic acid, propanedioic acid, butanedioic acid, 3-oxobutanoic acid, hydroxylamine-O-sulfonic acid, formamidine sulfinic acid, methylsulfamic acid, sulfoacetic acid, 1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid, nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid, monoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol, 1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene, tetrabutylammonium hydroxide, tetramethylammonium hydroxide, ammonium hydroxide, ammonium sulfamate, ammonium carbamate, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and combinations thereof. In an embodiment, the amount of the ligand stabilizer ranges from 0.001 wt. % to 20 wt. % based on the total weight of the photoresist composition. In an embodiment, the amount of metal oxide nanoparticles ranges from 1 wt. % to 10 wt. % based on the total weight of the photoresist composition. In an embodiment, the photoresist composition further includes a polymer resin and a photoactive compound. In an embodiment, the polymer resin includes one or more groups that will decompose when exposed to or react with bases, acids, or free radicals generated by the photoactive compound. In an embodiment, the photoactive compound is a photoacid generator, photobase generator, or a free-radical generator. In an embodiment, the photoresist composition includes from 0.001 wt. % to 1 wt. % of a surfactant.

Another embodiment of the disclosure is a method of forming a photoresist pattern including forming a photoresist layer comprising a photoresist composition over a substrate. The photoresist layer is selectively exposed to actinic radiation. The selectively exposed photoresist layer is developed to form a pattern in the photoresist layer. The photoresist composition includes metal oxide nanoparticles, a ligand, and an acid having an acid dissociation constant, pKa, of −15<pKa<4, or a base having a pKa of 40>pKa>9. In an embodiment, the actinic radiation is extreme ultraviolet radiation. In an embodiment, the photoresist composition includes a polymer resin and a photoactive compound. In an embodiment, the polymer resin includes one or more groups that will decompose when exposed to or react with bases, acids, or free radicals generated by the photoactive compound, and the photoactive compound is a photoacid generator, photobase generator, or a free-radical generator. In an embodiment, the method includes heating the photoresist layer after selectively exposing the photoresist layer.

The foregoing outlines features of several embodiments or examples so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments or examples introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A photoresist composition, comprising: a photoresist material including metal oxide nanoparticles and a ligand; and an acid having an acid dissociation constant, pKa, of −15<pKa<0.
 2. The photoresist composition of claim 1, wherein the amount of the acid ranges from 0.001 wt. % to 20 wt. % based on the total weight of the photoresist composition.
 3. The photoresist composition of claim 1, wherein the amount of metal oxide nanoparticles ranges from 1 wt. % to 10 wt. % based on the total weight of the photoresist composition.
 4. The photoresist composition of claim 1, wherein the metal oxide nanoparticles have an average particle size ranging from 1 nm to 10 nm.
 5. The photoresist composition of claim 1, wherein the metal oxide nanoparticles are selected from the group consisting of titanium dioxide, zinc oxide, zirconium dioxide, nickel oxide, cobalt oxide, manganese oxide, copper oxides, iron oxides, strontium titanate, tungsten oxides, vanadium oxides, chromium oxides, tin oxides, hafnium oxide, indium oxide, cadmium oxide, molybdenum oxide, tantalum oxides, niobium oxide, aluminum oxide, and combinations thereof.
 6. The photoresist composition of claim 1, wherein the ligand is a carboxylic acid or sulfonic acid ligand.
 7. The photoresist composition of claim 1, further comprising a polymer resin and a photoactive compound.
 8. A photoresist composition, comprising: a photoresist material including metal oxide nanoparticles and a ligand; an acid having an acid dissociation constant, pKa, of −15<pKa<0; and a ligand stabilizer, wherein the ligand stabilizer is selected from the group consisting of ethanedioic acid (oxalic acid), methanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, citric acid, uric acid, trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonic acid, methanesulfonic acid, maleic acid, carbonic acid, HNO₃, H₂SO₄, HCl, oxoethanoic acid, 2-hydroxyethanoic acid, propanedioic acid, butanedioic acid, 3-oxobutanoic acid, hydroxylamine-O-sulfonic acid, formamidine sulfinic acid, methylsulfamic acid, sulfoacetic acid, 1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid, nonafluorobutane-1-sulfonic acid, 5-sulfo salicylic acid, monoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol, 1H-benzotriazole, 1,2,4-triazole, ammonium hydroxide, ammonium sulfamate, ammonium carbamate, and combinations thereof.
 9. The photoresist composition of claim 8, wherein the amount of the ligand stabilizer ranges from 0.001 wt. % to 20 wt. % based on the total weight of the photoresist composition.
 10. The photoresist composition of claim 8, wherein the amount of metal oxide nanoparticles ranges from 1 wt. % to 10 wt. % based on the total weight of the photoresist composition.
 11. The photoresist composition of claim 8, further comprising a polymer resin and a photoactive compound.
 12. The photoresist composition of claim 11, wherein the polymer resin includes one or more groups that will decompose when exposed to or react with bases, acids, or free radicals generated by the photoactive compound.
 13. The photoresist composition of claim 12, wherein the photoactive compound is a photoacid generator, photobase generator, or a free-radical generator.
 14. The photoresist composition of claim 8, further comprising from 0.001 wt. % to 1 wt. % of a surfactant.
 15. The photoresist composition of claim 8, wherein an amount of the ligand stabilizer ranges from 1 wt. % to 10 wt. % based on a total weight of the photoresist composition.
 16. A method of forming a photoresist pattern, comprising: forming a photoresist layer comprising a photoresist composition over a substrate; selectively exposing the photoresist layer to actinic radiation; and developing the photoresist layer to form a pattern in the photoresist layer; wherein the photoresist composition includes: metal oxide nanoparticles; a ligand; and an acid having an acid dissociation constant, pKa, of −15<pKa<0.
 17. The method according to claim 16, wherein the actinic radiation is extreme ultraviolet radiation.
 18. The method according to claim 16, wherein the photoresist composition further comprises a polymer resin and a photoactive compound.
 19. The method according to claim 18, wherein the polymer resin includes one or more groups that will decompose when exposed to or react with bases, acids, or free radicals generated by the photoactive compound; and the photoactive compound is a photoacid generator, photobase generator, or a free-radical generator.
 20. The method according to claim 16, further comprising extending the pattern in the photoresist layer into the substrate. 